Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption

Hisao Kiuchi; Riku Shibuya; Takahiro Kondo; Junji Nakamura; Hideharu Niwa; Jun Miyawaki; Maki Kawai; Masaharu Oshima; Yoshihisa Harada

doi:10.1186/s11671-016-1344-6

Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption

Nanoscale Res Lett. 2016 Dec;11(1):127. doi: 10.1186/s11671-016-1344-6. Epub 2016 Mar 8.

Authors

Hisao Kiuchi¹, Riku Shibuya², Takahiro Kondo², Junji Nakamura², Hideharu Niwa^{3

4

5}, Jun Miyawaki^{3

4}, Maki Kawai¹, Masaharu Oshima⁴, Yoshihisa Harada^{6

7}

Affiliations

¹ Department of Applied Chemistry, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
² Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, Japan.
³ The Institute for Solid State Physics (ISSP), the University of Tokyo, Kashiwa, Chiba, Japan.
⁴ Synchrotron Radiation Research Organization, the University of Tokyo, Kashiwa, Chiba, Japan.
⁵ Present address: Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki, Japan.
⁶ The Institute for Solid State Physics (ISSP), the University of Tokyo, Kashiwa, Chiba, Japan. [email protected].
⁷ Synchrotron Radiation Research Organization, the University of Tokyo, Kashiwa, Chiba, Japan. [email protected].

Abstract

The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts.

Keywords: CO2 adsorption; Infrared reflection absorption spectroscopy; Lewis basicity; Nitrogen-doped carbon; X-ray absorption spectroscopy; X-ray photoelectron spectroscopy.